Image angle detection device and scan line interpolation device having the same

ABSTRACT

A binarizer binarizes a video signal input from an A/D converter and a video signal output from a line memory using an average luminance value provided from a detection window video signal processor as a threshold value, and outputs a binary pattern. A reference pattern generator generates a plurality of reference patterns. An angle detector compares the binary pattern with each of the plurality of reference patterns, and outputs the angle of a matched reference pattern as angle information. An arc shape detector outputs the edge angle information of a picture based on a combination of the angle information of an interpolation scanning line including an object interpolation pixel and the angle information of interpolation scanning lines above and below the interpolation scanning line.

TECHNICAL FIELD

The present invention relates to a picture angle detection apparatusthat detects the angle of a picture displayed based on a video signal, ascanning lines interpolation apparatus having the same and a pictureangle detection method.

BACKGROUND ART

In order to convert interlaced-scanning video signals intoprogressive-scanning video signals or convert progressive-scanning videosignals into enlarged or reduced video signals, an interpolation circuitthat carries out scanning lines interpolation is used. In theinterpolation circuit, the value of a pixel to be produced by theinterpolation (hereinafter referred to as “interpolation pixel”) iscalculated based on the values of pixels around the interpolation pixel.The angle of a picture having a diagonal edge or a thin diagonal linefor example is detected based on the luminance distribution ofsurrounding pixels and the value of the interpolation pixel iscalculated using pixels in the direction with a higher degree ofcorrelation.

Japanese Patent Laid-Open No. 9-37214 discloses a progressive scanninglines interpolation apparatus that can carry out scanning linesinterpolation in a picture having a diagonal edge.

The progressive scanning lines interpolation apparatus selects candidatesets of pixels for calculating the differential absolute value betweenpixel values from sets of original pixels located point-symmetricallyaround an interpolation pixel in order to convert an interlaced-scanningvideo signal into a progressive-scanning video signal. The differentialabsolute values between the values of the selected sets of pixels areeach calculated. Then, based on the edge information of these sets ofthe original pixels, the differential absolute values are corrected, aset of original pixels whose corrected differential absolute value isminimum is detected, and the interpolation pixel is produced based onthe detected set of original pixels.

In this way, a picture having a diagonal edge can be subjected toscanning lines interpolation.

The conventional progressive scanning lines interpolation apparatushowever cannot determine whether the edge of the picture is a straightline shape or a curved shape such as an arc. Therefore, a picture havinga curved edge such as an arc shape cannot be formed into a smoothpicture by interpolation.

DISCLOSURE OF THE INVENTION

An object of the invention is to provide a picture angle detectionapparatus that can accurately detect the angle and shape of a picturedisplayed based on a video signal.

Another object of the invention is to provide a scanning linesinterpolation apparatus that can carry out interpolation suitable forthe angle and shape of a picture displayed based on a video signal.

Further object of the invention is to provide a picture angle detectionmethod that can accurately detect the angle and shape of a picturedisplayed based on a video signal

A picture angle detection apparatus for detecting the angle of a picturerelated to a pixel to be interpolated in each interpolation scanningline between scanning lines based on an input video signal according toone aspect of the invention comprises a binary pattern generator thatbinarizes the input video signal in a predetermined detection regionincluding a plurality of scanning lines and the pixel to be interpolatedto generate a binary pattern, a reference pattern generator thatgenerates binary pictures having different directions as a plurality ofreference patterns, a comparator that compares the binary patterngenerated by the binary pattern generator with each of the plurality ofreference patterns to detect the angle of the picture related to thepixel to be interpolated based on the comparison result, and a shapedetector that detects the shape of the picture based on the combinationof the angle of the picture detected by the comparator related to thepixel to be interpolated and angles of the picture detected in upper andlower interpolation scanning lines above and below the pixel.

In the picture angle detection apparatus according to the invention, thebinary pattern generator binarizes an input video signal in apredetermined detection region to generate a binary pattern. Thereference pattern generator generates binary pictures having differentdirections as a plurality of reference patterns. The comparator comparesthe binary pattern with each of the plurality of reference patterns todetect the angle of the picture related to the pixel to be interpolatedbased on the comparison result. The shape detector detects the shape ofthe picture based on the combination of the angle of the picturedetected by the comparator related to the pixel to be interpolated andangles of the picture detected in the upper and lower interpolationscanning lines.

In this way, two-dimensional patterns are compared, and erroneousdetection can be less than the case of using the differential valuebetween two pixels, so that the angle of a diagonal edge of a picturecan be detected accurately. Using the two-dimensional referencepatterns, the angle to be detected is not limited to angles formed bystraight lines connecting pixels in point-symmetry around theinterpolation pixel, and angles between these angles can be detected.Consequently, the angles can be detected by smaller steps.

The approach to compare a binary pattern with a plurality of referencepatterns for detecting the curved shape of a picture at a time wouldrequire an enormous number of reference patterns including at leastthree scanning lines. This could increase the scale of the circuit andcould hardly be practical. In the picture angle detection apparatusaccording to the invention, local angles of a picture are detected in asmall area for each pixel to be interpolated between interpolationscanning lines, and the shape of the picture is detected based on thecombination of the detected angles above and below. In this case, theshape of the picture can be detected by partly improving theconfiguration for detecting the angle of the picture by comparing abinary pattern with a plurality of reference patterns.

Consequently, the detection of the shape of the picture does not delaythe process of detecting the angle of the picture, and the angle andshape of the picture can be detected accurately without increasing thescale of the circuit.

Provided that the angle of the picture detected by the comparatorrelated to the pixel to be interpolated is between the angle of thepicture detected in the upper interpolation scanning line and the angleof the picture detected in the lower interpolation scanning line, andthe absolute value of the angle of the picture detected in the upperinterpolation scanning line is larger than the absolute value of theangle of the picture detected in the lower interpolation scanning line,the shape detector may output a shape detection signal indicating thatthe shape of the picture is convex toward the lower right, when theangle of the picture detected related to the pixel to be interpolated,and the angle of the picture detected in the upper interpolationscanning line and the angle of the picture detected in the lowerinterpolation scanning line are positive values, while the shapedetector may output a shape detection signal indicating that the shapeof the picture is convex toward the lower left, when the angle of thepicture detected related to the pixel to be interpolated, and the angleof the picture detected in the upper interpolation scanning line and theangle of the picture detected in the lower interpolation scanning lineare negative values. Meanwhile, provided that the angle of the picturedetected by the comparator related to the pixel to be interpolated isbetween the angle of the picture detected in the upper interpolationscanning line and the angle of the picture detected in the lowerinterpolation scanning line, and the absolute value of the angle of thepicture detected in the upper interpolation scanning line is smallerthan the absolute value of the angle of the picture detected in thelower interpolation scanning line, the shape detector may output a shapedetection signal indicating that the shape of the picture is convextoward the lower left, when the angle of the picture detected by thecomparator related to the pixel to be interpolated, and the angle of thepicture detected in the upper interpolation scanning line and the angleof the picture detected in the lower interpolation scanning line arepositive values, while the shape detector may output a shape detectionsignal indicating that the shape of the picture is convex toward theupper right, when the angle of the picture detected related to the pixelto be interpolated, and the angle of the picture detected in the upperinterpolation scanning line and the angle of the picture detected in thelower interpolation scanning line are negative values.

In this way, the direction in which the picture has a convex shape canbe detected depending on the combination of the angle of the picturedetected related to the pixel to be interpolated and angles detected inthe upper and lower interpolation scanning lines.

When the shape detector detects that the shape of the picture is an arc,the detector may output a shape detection signal indicating thedirection of the inside of the arc.

In this way, the direction of the arc in the picture having the arcshape can be determined based on the shape detection signal indicatingthe inside of the arc.

The binary pattern generator may include a threshold value calculationdevice that calculates a threshold value for binarization based on theluminance of a video signal in the detection region, and a binarizerthat binarizes the input video signal using the threshold valuecalculated by the threshold value calculation device to generate thebinary pattern.

In this way, the threshold value for binarization is calculated based onthe luminance of the video signal in the detection region, and thereforethe binary pattern can be generated without an externally set thresholdvalue and irrespective of the luminance level of the video signal.

The picture angle detection apparatus may further comprise a determiningdevice that determines whether or not the luminance distribution in thehorizontal direction of scanning lines is in the form of a monotonousincrease or decrease in the video signals in the detection region, andthe comparator may not compare the binary pattern with each of theplurality of reference patterns when the luminance distribution isneither in the form of a monotonous increase nor a monotonous decrease.

When the luminance distribution in the horizontal direction of thescanning lines is not in the form of a monotonous increase or decreasein the video signal in the detection region, the binary pattern is notcompared to each of the plurality of reference patterns, and the angleof the picture is not detected. In this way, erroneous detection causedby noise can be reduced.

The picture angle detection apparatus may further comprise a contrastdetector that detects a contrast in the video signal in the detectionregion, and the comparator may not compare the binary pattern with eachof the plurality of reference patterns when the contrast detected by thecontrast detector is smaller than a predetermined value.

When the contrast in the video signal is low, the effect ofinterpolation processing with diagonally located pixels is small.Therefore, when the contrast in the video signal in the detection regionis smaller than a predetermined value, the binary pattern is notcompared with each of the plurality of reference patterns and the angleof the picture is not detected. In this way, the interpolationprocessing with diagonally located pixels that causes noises may becarried out only when there can be a great effect.

The plurality of reference patterns each include a first pixel rowarranged in a scanning line above the pixel to be interpolated and asecond pixel row arranged in a scanning line below the pixel to beinterpolated, the first pixel row has one transition point from a firstpixel value to a second pixel value, the second pixel row has onetransition point from a first pixel value to a second pixel value, andthe transition direction from the first pixel value to the second pixelvalue in the first pixel row and the transition direction from the firstpixel value to the second pixel value in the second pixel row may be thesame.

In this reference pattern, the pixel row in the upper scanning line andthe pixel row in the lower scanning line both have a luminance changeand a luminance gradient in the same direction. The reference patterncorresponds to a picture with a diagonal edge. Consequently, when thebinary pattern is matched with a reference pattern, the angle of thediagonal edge can surely be specified.

A scanning lines interpolation apparatus according to another aspect ofthe invention comprises a picture angle detection apparatus that detectsthe angle and shape of a picture related to a pixel to be interpolatedbased on an input video signal, and an interpolation circuit thatselects pixels to be used for interpolation based on the angle and shapedetected by the picture angle detection apparatus, and calculates thevalue of the pixel to be interpolated using the selected pixels togenerate an interpolation scanning line. The picture angle detectionapparatus includes a binary pattern generator that binarizes the inputvideo signal in a predetermined detection region including a pluralityof scanning lines and a pixel to be interpolated in each scanning lineto generate a binary pattern, a reference pattern generator thatgenerates binary pictures having different directions as a plurality ofreference patterns, a comparator that compares the binary patterngenerated by the binary pattern generator with each of the plurality ofreference patterns generated by the reference pattern generator todetect the angle of the picture related to the pixel to be interpolatedbased on the result of comparison, and a shape detector that detects theshape of the picture based on the combination of the angle of thepicture detected by the comparator related to the pixel to beinterpolated and the angles of the picture detected in upper and lowerinterpolation scanning lines.

In the scanning lines interpolation apparatus according to theinvention, the angle detection apparatus surely detects the angle andshape of the picture related to the pixel to be interpolated based on aninput video signal, and pixels to be used for interpolation are selectedbased on the angle and shape detected by the picture angle detectionapparatus. Using the selected pixels, the interpolation circuitcalculates the value of the pixel to be interpolated to generate aninterpolation scanning line.

In this way, the pixels to be used for interpolation are selecteddepending on the shape of the picture, and therefore not only straightline shapes but also curved, diagonal edges may smoothly beinterpolated.

Consequently, smooth interpolation suitable for the angle and shape ofthe picture displayed based on the video signal can be carried out.

When the shape detector detects that the shape of the picture is an arc,the detector may output a shape detection signal indicating thedirection of the inside of the arc, and the interpolation circuit mayselect pixels to be used for interpolation from the inside of the arcbased on the shape detection signal output from the shape detector andcalculate the value of the pixel to be interpolated using the selectedpixels to generate an interpolation scanning line.

In this way, the pixels to be used for interpolation are selected fromthe inside of the arc based on the shape detection signal indicating thedirection of the inside of the arc, and the value of the pixel to beinterpolated is calculated using the selected pixels. Therefore, smoothinterpolation along the shape of the arc can be carried out.

When the shape detector detects that the shape of the picture is an arc,the detector may output a shape detection signal indicating thedirection of the inside of the arc. The interpolation circuit may selectpositions shifted in the direction of the inside of the arc by 0.5 pixelfrom positions in the upper and lower scanning lines in the direction ofthe angle of the picture detected for the pixel to be interpolated andcalculate the value of the pixel to be interpolated using the values ofthe pixels in the selected positions in order to generate aninterpolation scanning line.

In this way, the pixels to be used for interpolation are selected fromspecified pixels within the inside of the arc based on the shapedetection signal indicating the inside of the arc. The value of thepixel to be interpolated is then calculated using the selected pixels.Therefore, smooth interpolation along the shape of the arc can becarried out.

Furthermore, the pixels to be used for interpolation can be selecteddepending on the shape of the arc, and therefore not only straight lineshapes but also diagonal edges of arc shapes may smoothly beinterpolated.

A picture angle detection method for detecting the angle of a picturerelated to a pixel to be interpolated in each interpolation scanningline between scanning lines based on an input video signal according tofurther aspect of the invention comprises the steps of binarizing theinput video signal in a predetermined detection region including aplurality of scanning lines and the pixel to be interpolated to generatea binary pattern, generating binary pictures having different directionsas a plurality of reference patterns, comparing the generated binarypattern with each of the generated plurality of reference patterns todetect the angle of the picture related to the pixel to be interpolatedbased on the comparison result, and detecting the shape of the picturebased on the combination of the detected angle of the picture related tothe pixel to be interpolated and angles of the picture detected in upperand lower interpolation scanning lines above and below the pixel.

In the picture angle detection method according to the invention, aninput video signal in a predetermined detection region is binarized togenerate a binary pattern. Binary pictures having different directionsare generated as a plurality of reference patterns. The binary patternis compared with each of the plurality of reference patterns to detectthe angle of the picture related to the pixel to be interpolated basedon the comparison result. The shape of the picture is detected based onthe combination of the angle of the detected picture related to thepixel to be interpolated and angles of the picture detected in the upperand lower interpolation scanning lines.

In this way, two-dimensional patterns are compared, and erroneousdetection can be less than the case of using the differential valuebetween two pixels, so that the angle of a diagonal edge of a picturecan be detected accurately. Using the two-dimensional referencepatterns, the angle to be detected is not limited to angles formed bystraight lines connecting pixels in point-symmetry around theinterpolation pixel, and angles between these angles can be detected.Consequently, the angles can be detected by smaller steps.

Local angles of a picture are detected in a small area for each pixel tobe interpolated between interpolation scanning lines, and the shape ofthe picture is detected based on the combination of the detected anglesabove and below. In this case, the shape of the picture can be detectedby partly improving the configuration for detecting the angle of thepicture by comparing a binary pattern with a plurality of referencepatterns.

Consequently, the detection of the shape of the picture does not delaythe process of detecting the angle of the picture, and the angle andshape of the picture can be detected accurately without increasing thescale of the circuit.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram showing the configuration of a picture angledetection apparatus according to an embodiment of the invention;

FIG. 2 is a schematic diagram showing an example of a binary patternoutput from a binarizer in the apparatus;

FIGS. 3 to 6 are schematic diagrams each showing an example of referencepatterns generated by the reference pattern generator shown in FIG. 1;

FIG. 7 is a table for use in illustration of processing by the arc shapedetector in FIG. 1;

FIG. 8 is a block diagram showing the configuration of a scanning linesinterpolation apparatus including the picture angles detection apparatusshown in FIG. 1;

FIG. 9 is a block diagram showing the configuration of an interpolationcircuit in the scanning lines interpolation apparatus shown in FIG. 8;

FIG. 10 is a schematic diagram showing an example of the angles of apicture detected by the picture angle detection apparatus shown in FIG.1;

FIG. 11 is a schematic diagram showing an example of interpolation ofpixels using the angle information and arc shape information of apicture detected by the picture angle detection apparatus shown in FIG.1; and

FIG. 12 is a schematic diagram showing an example of interpolation ofpixels using the angle information of a picture detected by the pictureangle detection apparatus shown in FIG. 1.

BEST MODE FOR CARRYING OUT THE INVENTION

FIG. 1 is a block diagram of the configuration of a picture angledetection apparatus according to an embodiment of the invention.

The picture angle detection apparatus 10 shown in FIG. 1 includes linememories 1 a, 1 b, and 1 c, a binarizer 2, an angle detector 3, an arcshape detector 4, a detection window video signal processor 5, areference pattern generator 6, and an A/D (analog/digital) converter 7.

The A/D converter 7 converts an analog video signal VA into a digitalvideo signal VD1 for output. The video signal VD1 output from the A/Dconverter 7 is input into the line memory 1 a and the binarizer 2 andthe detection window video signal processor 5. The line memory 1 adelays the video signal VD1 output from the A/D converter 7 by onescanning line for output. The video signal VD2 thus output from the linememory 1 a is provided to the binarizer 2 and the detection window videosignal processor 5.

In this example, the video signals VD1 and VD2 have 256 gray scaleluminance levels. More specifically, the minimum luminance value for thevideo signals VD1 and VD2 is “0” and the maximum value is “255”.

The binarizer 2 binarizes the video signal VD1 output from the A/Dconverter 7 and the video signal VD2 output from the line memory 1 ausing an average luminance value LU applied from the detection windowvideo signal processor 5 that will be described and outputs a binarypattern BI of “1” and “0”. The binary pattern BI has a size equal tothat of the detection window.

Here, the detection window is for example a rectangular region including7×2 pixels, seven pixels of which are from the video signal VD1 and theremaining seven pixels are from the video signal VD2, or a rectangularregion including 15×2 pixels, 15 pixels of which are from the videosignal VD1 and the remaining 15 pixels are from the video signal VD2.Note that in the following description, the size of the detection windowis 9×2 pixels. In this case, the size of the binary pattern BI is also9×2 pixels. The size of the detection window is not limited to these,which can be set arbitrarily within the scope of the invention.

The detection window video signal processor 5 sets a detection windowfor the input video signal VD1 and the video signal VD2 output from theline memory 1 a, calculates the average luminance value of the videosignals VD1 and VD2 in the detection window, and provides the resultingaverage luminance value LU to the binarizer 2 as a threshold value forbinarization.

Note that according to the embodiment, the average luminance value ofall the pixels in the detection window is used as the threshold forbinarization. However, the average value between the maximum and minimumvalues of the pixels in the detection window or the middle number in thesequence of luminance values in the order of magnitude may be used asthe threshold value. Alternatively, the average luminance value of aplurality of pixels whose values are close to the middle number in thesequence of luminance values in the order of magnitude may be used asthe threshold value for binarization.

The detection window video signal processor 5 determines whether or notthe horizontal luminance distribution of the video signals VD1 and VD2in the detection window is in the form of a monotonous increase ordecrease. When the distribution is not in the form of a monotonousincrease or decrease, the minimum value “0” or the maximum value “255”may be provided to the binarizer 2 as a threshold value. Then, thebinarizer 2 outputs a binary pattern BI of all “1” or “0”. In this case,the differential value between two adjacent pixels in the video signalsVD1 and VD2 may be calculated sequentially, and if the differentialvalues have the same sign, it could be determined that the distributionis in the form of a monotonous increase or decrease.

The detection window video signal processor 5 calculates the differencebetween the maximum and minimum luminance values of the video signalsVD1 and VD2 in the detection window as a contrast. Then, when thecalculated contrast is lower than a predetermined value, the minimumvalue “0” or the maximum value “255” is provided to the binarizer 2. Inthis way, the binarizer 2 outputs a binary pattern BI of all “1” or “0”.

The reference pattern generator 6 generates a plurality of referencepatterns RA of “1” and “0” and applies the patterns to the angledetector 3. The reference patterns RA each have a size equal to that ofthe detection window.

The angle detector 3 compares the binary pattern BI provided from thebinarizer 2 with each of the plurality of reference patterns RA providedfrom the reference pattern generator 6 and outputs the angle of amatched one of the reference patterns RA as angle information S1. Theangle will later be described. Now, the comparison operation between thebinary pattern BI and the reference patterns RA will be referred to as“pattern matching”.

As described above, if the luminance distributions of the video signalsVD1 and VD2 in the detection window are both not in the form of amonotonous increase or decrease, a binary pattern BI of all “1” or “0”may be output from the binarizer 2. In this case, the angle informationS1 is not output from the angle detector 3.

When the contrast in the video signals VD1 and VD2 in the detectionwindow is lower than the predetermined value, a binary pattern BI of all“1” or “0” is output from the binarizer 2, and therefore the angleinformation S1 is not output from the angle detector 3.

When the contrast in the video signals VD1 and VD2 is low, the effect ofinterpolation using diagonally located pixels is small. In interpolationusing diagonally located pixels, noises could be caused unless anglesare not accurately detected. Therefore, when the effect is low, theangle information S1 is not output so that the interpolation usingdiagonally located pixels is not carried out.

The line memory 1 b outputs angle information S2 delayed by one scanningline from the angle information S1 output from the angle detector 3 tothe arc shape detector 4 and the line memory 1 c. The line memory 1 capplies angle information S3 delayed by one scanning line from the angleinformation S2 output from the line memory 1 b to the arc shape detector4.

Here, a scanning line including an interpolation pixel will be referredto as “interpolation scanning line”. The arc shape detector 4 outputspicture edge angle information T1 based on the combination of the angleinformation S3 of an interpolation scanning line one line above theobject interpolation scanning line, the angle information S1 of aninterpolation scanning line one line below the object interpolationscanning line, and the angle information S2 of the object interpolationscanning line. The arc shape detector 4 also recognizes the arc shapeand outputs arc shape information T2. Note that the angle detection andthe arc shape recognition will be detailed later.

FIG. 2 is a schematic diagram showing an example of the binary patternBI output from the binarizer 2 shown in FIG. 1.

In FIG. 2, IN represents an interpolation pixel and IL represents aninterpolation scanning line. Also in the figure, AL represents ascanning line one line above the interpolation scanning line IL, whileBL represents a scanning line one line below the interpolation scanningline IL.

In the example in FIG. 2, the low luminance part (dark part) isindicated by “0” and the high luminance part (bright part) is indicatedby “1”. In the binary pattern BI, the angle of the edge of a picture is45°. Here, the horizontal angle is 0 and the angle in the upper rightdiagonal direction is positive.

FIGS. 3, 4, 5, and 6 are schematic diagrams each showing an example ofreference patterns generated by the reference pattern generator 6 inFIG. 1. The shadowed pixels are pixels in the upper and lower scanninglines that are used for calculating values of interpolation pixelsindicated by bold squares.

In FIGS. 3, (a), (b), (c), (d), (e), and (f) are reference patterns for45°, 34°, 27°, 22°, 18°, and 16°, respectively. In the example in FIG.3, the upper left part is a dark part and the lower right part is abright part. In FIGS. 4, (a), (b), (c), (d), (e), and (f) are referencepatterns for 45°, 34°, 27°, 22°, 18°, and 16°, respectively. In theexample in FIG. 4, the upper left part is a bright part and the lowerright part is a dark part.

In FIGS. 5, (a), (b), (c), (d), (e), and (f) are reference patterns for−45°, −34°, −27°, −22°, −18°, and −16°, respectively. In the example inFIG. 5, the upper right part is a dark part and the lower left part is abright part. In FIGS. 6, (a), (b), (c), (d), (e), and (f) are referencepatterns for −45°, −34°, −27°, −22°, −18°, and −16°, respectively. Inthe example in FIG. 6, the upper right part is a bright part and thelower left part is a dark part.

The reference patterns shown in FIGS. 3 to 6 are compared with thebinary pattern BI output from the binarizer 2 at the angle detector 3,and the angle detector 3 outputs the angle information S1 of thereference pattern matched with the pattern BI.

In addition, as shown in FIGS. 3 to 6, in the reference patterns basedon two-dimensional luminance distribution, not only angles betweenstraight lines connecting pixels located in point-symmetrical positionsaround the interpolation pixel but also angles between these angles maybe set. For example, angles 34° and 22° between 45°, 27°, and 18° can beset.

The binary pattern BI in FIG. 2 for example can be matched with one ofthe six reference patterns at (a) in FIG. 4. In this case, the angledetector 3 in FIG. 1 outputs 45° indicated by the reference pattern at(a) in FIG. 4 as the angle information S1. Note that the referencepatterns RA generated by the reference pattern generator 6 in FIG. 1 mayhave an arbitrary size other than those of the examples shown in FIG. 6.

FIG. 7 is a table for use in illustration of processing by the arc shapedetector 4 in FIG. 1. The table in FIG. 7 includes detected angles forinterpolation pixels, and examples of arc shapes recognized based oncombinations of detected angles in a lower interpolation scanning lineand an upper interpolation scanning line.

More specifically, the arc shapes are divided into five cases ofcombinations A, B, C, D, and E.

In Case A in FIG. 7, the edge of the arc (arc edge) has a convex shapedirected to the “lower right”, and the inside of the arc is directed tothe “left”. In this case, the absolute value of the detected angle ofthe interpolation pixel is the intermediate value between the absolutevalues of the detected angle in the lower and upper interpolationscanning lines. The absolute value of the detected angle in the upperinterpolation scanning line is larger than the absolute value of thedetected angle in the lower interpolation scanning line and all thedetected angles are positive values.

The arc shape detector 4 outputs the detected angle of the interpolationpixel as angle information T1. When an arc shape is recognized, thedirection of the inside of the arc shape is output as arc shapeinformation T2.

FIG. 7 shows schematic arc shapes and the directions of the inside ofthe arc shapes in the right most column by way of illustration. The setsof thin connected arrows are each recognized as an arc, and thedirection of each of the thin arrows indicates an angle detected alongthe arc, and thick arrows indicate the insides of the arcs.

Similarly to Case A in FIG. 7, in the combination cases B, C, and D, thedirection of the convex shape of the arc edge and the direction of theinside of the arc shape are shown.

In Case B in FIG. 7, the direction of the convex shape of the arc edgeis the “upper right” and the direction of the inside is the “left”. Inthis case, the absolute value of the detected angles of theinterpolation pixel is the intermediate value between the absolutevalues of the detected angles in the lower and upper interpolationscanning lines. The absolute value of the detected angle in the upperinterpolation scanning line is smaller than the absolute value of thedetected angle in the lower interpolation scanning line and all thedetected angles are negative values.

In the combination in Case C in FIG. 7, the direction of the convexshape of the arc edge is the “upper left” and the direction of theinside of the arc shape is the “right”. In this case, the absolute valueof the interpolation pixel is the intermediate value between theabsolute values of the detected angles in the lower and upperinterpolation scanning lines. The absolute value of the detected anglein the upper interpolation scanning line is smaller than the absolutevalue of the detected angle in the lower interpolation scanning line andall the detected angles are positive values.

In the combination in Case D in FIG. 7, the direction of the convexshape of the arc edge is the “lower left” and the direction of theinside of the arc shape is the “right”. In this case, the absolute valueof the detected angle of the interpolation pixel is the intermediatevalue between the absolute values of the detected angle in the lower andupper interpolation scanning lines. The absolute value of the detectedangles in the upper interpolation scanning line is smaller than theabsolute value of the detected angle in the lower interpolation scanningline and all the detected angles are negative values.

In Case E in FIG. 7, the combination of detected angles cannot berecognized as that of an arc shape. More specifically, any combinationsnot belonging to the combinations in Cases A, B, C, and D all belong toCase E in FIG. 7.

Note that the intermediate value is defined as any value between twovalues X and Y, and larger than X and smaller than Y when X<Y.

The reference position for a detected angle in the upper interpolationscanning line corresponds to a single point in the direction determinedbased on the detected angle of the interpolation pixel in the upperinterpolation scanning line relative to the interpolation pixel. Thereference position for the detected angle in the lower interpolationscanning line corresponds to a single point in the direction determinedbased on the detected angle of the interpolation pixel in the upperinterpolation scanning line relative to the interpolation pixel.

The reference position for a detected angle in the upper interpolationscanning line may be a horizontal region (of a plurality of pixels)having a predetermined width including a point in the directiondetermined based on the detected angle of the interpolation pixel in theupper interpolation scanning line relative to the interpolation pixel.The reference position for a detected angle in the lower interpolationscanning line may be a horizontal region (of a plurality of pixels)having a predetermined width including a point in the directiondetermined based on the detected angle of the interpolation pixel in thelower interpolation scanning line relative to the interpolation pixel.

Note that the combinations of the detected angle of the interpolationpixel, and the detected angles in the upper and lower interpolationscanning lines as shown in FIG. 7 are only by way of illustration, andby no means intended as being restrictive. Combinations other than thoseshown may be employed.

In the picture angle detection apparatus 10 according to the embodiment,the luminance distribution of the video signals VD1 and VD2 in thedetection widow is converted into the binary pattern BI. Then, thebinary pattern BI is compared for pattern matching with a plurality ofpreset reference patterns RA, so that the angle of a diagonal edge in apicture can be detected with a small scale circuit configuration.

In this way, the average luminance value in the detection window is usedas the threshold value for binarization, and therefore a binary patternBI including both “0” and “1” can always be produced regardless of theluminance level of the picture and without an externally set binarythreshold value.

Since the pattern matching is carried out based on the two-dimensionalluminance distribution, erroneous detection can be less than the case ofusing the differential value between two pixels, so that the angle of adiagonal edge of a picture can be detected accurately.

Using the reference patterns RA based on the two-dimensional luminancedistribution, the angle to be detected is not limited to an angle formedby straight lines connecting pixels in point-symmetry around theinterpolation pixel, and angles between these angles can be detected.Consequently, the angles can be detected at smaller intervals using theline memory 1 a with a smaller capacity.

Since an arc shape can be recognized based on the combination of thedetected angle of the interpolation pixel, and the detected angles ofthe upper and lower interpolation scanning lines, reference patternsthat require three or more scanning lines are not necessary.Consequently, the angle of a picture can be detected and the arc shapecan be recognized without increasing the circuit scale of the pictureangle detection apparatus 10 or the calculation range by the apparatus.

FIG. 8 is a block diagram showing the configuration of a scanning linesinterpolation apparatus including the picture angle detection apparatusshown in FIG. 1.

In FIG. 8, the scanning lines interpolation apparatus 100 includes thepicture angle detection apparatus 10 and an interpolation circuit 20. Avideo signal VA is input to the picture angle detection apparatus 10 andthe interpolation circuit 20.

The picture angle detection apparatus 10 has the same configuration asthat of the picture angle detection apparatus 10 shown in FIG. 1. Thepicture angle detection apparatus 10 detects the angle of a diagonaledge or an arc shape of a picture based on the video signal VA, andoutputs angle information T1 and arc shape information T2. Theinterpolation circuit 20 selects pixels from the upper and lowerscanning lines in a diagonal direction relative to the interpolationpixel based on the angle information T1 and the arc shape informationT2, calculates the luminance value of the interpolation pixel using theluminance values of the selected pixels, and outputs an interpolationvideo signal VOUT.

In the scanning lines interpolation apparatus 100 shown in FIG. 8, theangles of a picture whose edge in a diagonal direction includes not onlya straight line shape but also an arc shape can accurately be detected,and the arc shape can be recognized. Therefore, for the picture whoseedge in a diagonal direction includes not only a straight line shape butalso an arc shape, suitable pixels in the diagonal direction can beselected to carry out smooth interpolation.

FIG. 9 is a block diagram of the configuration of the interpolationcircuit 20 in the scanning lines interpolation apparatus 100 shown inFIG. 8.

The interpolation circuit 20 in FIG. 9 includes an A/D (analog/digital)converter 21, a line memory 22, an interpolation pixel selection circuit23, and an average value operation circuit 24.

The A/D converter 21 converts an analog video signal VA into a digitalvideo signal VD1 for output. The video signal VD1 output from the A/Dconverter 21 is input into the line memory 22 and the interpolationpixel selection circuit 23. The line memory 22 delays the video signalVD1 output from the A/D converter 21 by one scanning line for output.The video signal VD2 thus output from the line memory 22 is provided tothe interpolation pixel selection circuit 23.

Using the provided video signals VD1 and VD2, and the angle informationT1 and the arc shape information T2 in the picture angle detectionapparatus 10, the interpolation pixel selection circuit 23 selects aninterpolation reference pixel P1 from the upper scanning line for outputand an interpolation reference pixel P2 from the lower scanning line foroutput to the average value operation circuit 24.

The average value operation circuit 24 calculates and outputs theluminance value of the interpolation pixel based on the interpolationreference pixels P1 and P2.

The interpolation pixel selection circuit 23 selects these interpolationreference pixels so that edges in a picture can be smoothed byinterpolation. The interpolation pixel selection circuit 23 performsselectively the operation for the case when the picture has a straightline shaped edge and the operation for the case when the picture has anarc shaped edge. When the picture has a straight line shaped edge, theinterpolation pixel selection circuit 23 selects pixels in the shadowedpart in FIGS. 3 to 6 from the upper and lower scanning lines asinterpolation reference pixels. The center positions of theinterpolation reference pixels are interpolation reference positions.Meanwhile, when the picture has an arc shaped edge, the interpolationpixel selection circuit 23 specifies positions in the direction relativeto the interpolation pixel indicated by the angle information T1, andselects positions shifted horizontally within the inside of the arcshape as the interpolation reference positions based on the arc shapeinformation T2.

With reference to FIG. 7, for example, when the arc shape in Case A isdetected, the direction of the inside of the arc is the left as denotedby the thick arrow, and therefore the interpolation pixel selectioncircuit 23 specifies positions in the direction indicated by the angleinformation T1 in the upper and lower scanning lines relative to theinterpolation pixel, and selects the interpolation reference positionsfrom positions shifted to the left from the specified positions.

It has been confirmed through experiments that for a picture with an arcshape, the arc shape is most smoothly formed by interpolation when thepositions 0.5 pixel shifted from the interpolation reference positionsselected for the picture having a straight line shaped edge are selectedas the interpolation reference positions.

The average value operation circuit 24 calculates the average luminancevalue of the pixels including the interpolation reference positions todetermine the luminance value of the interpolation pixel. Although notshown, the average value operation circuit 24 includes a correlationoperation circuit and may carry out interpolation operationcorresponding to the correlation degree, i.e., the difference betweenthe pixels including the interpolation reference positions. In this way,if the angle or arc shape is detected erroneously for some reason, anoise caused by interpolation can be reduced.

FIG. 10 shows an example of angle information of a picture detected bythe picture angle detection apparatus 10 shown in FIG. 1. An example ofa picture having an arc-shaped edge is shown in FIG. 10. FIG. 11 showsan example of interpolation of pixels using the angle information andarc shape information of the picture detected by the picture angledetection apparatus 10 shown in FIG. 1. In comparison, FIG. 12 shows anexample of interpolation of pixels using only the angle information ofthe picture detected by the picture angle detection apparatus 10 shownin FIG. 1.

In FIGS. 10 to 12, IL1, IL2 and IL3 represent interpolation scanninglines. Also in the figures, AL, BL, CL, and DL represent scanning lines.In FIGS. 10 to 12, the values on the scanning lines AL, BL, CL, and DLrepresent the luminance values of the pixels. In FIG. 10, the values onthe interpolation scanning lines IL1, IL2, and IL3 are the luminancevalues of interpolation pixels. In FIGS. 11 and 12, the values on theIL1, IL2, and IL3 represent the luminance values of the interpolationpixels.

Here, IN is an interpolation pixel of interest. In this case, IL2represents an object interpolation scanning line, BL is a scanning lineabove the interpolation scanning line, CL is a scanning line below theinterpolation scanning line, IL1 is an upper interpolation scanning lineand IL3 is a lower interpolation scanning line. In FIGS. 11 and 12, theinterpolation reference positions P1, P2, P3 and P4 are denoted by x. Inthe example in FIG. 10, the angle of the object interpolation pixel INrelative to the picture is 27°.

In the example in FIG. 12, the positions directed at 27° to theinterpolation pixel IN are selected as interpolation reference positionsP3 and P4 in the upper and lower scanning lines BL and CL. The luminancevalues of the pixels Q3 and Q4 including interpolation referencepositions P3 and P4 are both “100” and therefore the luminance value ofthe interpolation pixel IN is “100” after interpolation operation usingthe pixels Q3 and Q4 including the interpolation reference positions P3and P4. The luminance values of the other interpolation pixels arecalculated in the same manner, so that the processing result as shown inFIG. 12 is provided.

In the example in FIG. 11, R1 and R2 represent reference pixels for theupper and lower interpolation scanning lines IL1 and IL3, respectively.The angle information of the reference pixel R1 is 45° and the angleinformation of the reference pixel R2 is 18°. Therefore, the example inFIG. 11 corresponds to Case A in FIG. 7, and the direction of the insideof the arc shape is the left. Consequently, the positions p1 and p2 at27° relative to the interpolation pixel IN are specified in the upperand lower scanning lines BL and CL, and the positions 0.5 pixel shiftedhorizontally to the left from these specified positions p1 and p2 areselected as the interpolation reference positions P1 and P2. Theluminance values of the pixels including the interpolation positions P1and P2 are each the average luminance value between the luminance values“100” and “0” of two adjacent pixels Q11 and Q12; Q13 and Q14, in otherwords, the luminance values are both “50”. Therefore, the luminancevalue of the interpolation pixel IN is “50” after interpolationoperation using the pixels including the interpolation referencepositions P1 and P2. The luminance values of the other interpolationpixels are calculated in the same manner, so that the result as shown inFIG. 11 is provided.

Note that in FIGS. 11 and 12, the values on the interpolation scanninglines IL1, IL2, and IL3 are the luminance values of interpolationpixels, solid circles each represent the intermediate luminance valuefor each scanning line, and the dotted line connects the points of theintermediate luminance values. More specifically, the dotted linerepresents the edge of the picture. In this example, the intermediatevalue is a luminance value of “50”.

In comparison with the result in FIG. 11, the edge shape of the pictureafter interpolation is bent when the luminance values of theinterpolation pixels are calculated only with the angle information ofthe picture as shown in FIG. 12 and a smooth edge cannot be provided bythe interpolation. More specifically, the interpolation in FIG. 12 iscarried out in the locally recognized angle directions, and therefore isnot necessarily smooth in terms of overall continuity.

In contrast, when the luminance values of the interpolation pixels arecalculated based on the angle information and arc shape information ofthe picture as shown in FIG. 11, a smooth edge approximated to the arcshape can be formed.

Note that in this example, the interpolation reference positions areshifted by 0.5 pixel when an arc shape is recognized, but the inventionis not limited to this, and the shift amount can be set as required.

According to the embodiment, the binarizer 2 and the detection windowvideo signal processor 5 correspond to a binary pattern generator, thereference pattern generator 6 to a reference pattern generator and theangle detector 3 to a comparator. The arc shape detector 4 correspondsto a shape detector. The detection window video signal processor 5corresponds to a threshold value calculation device and a determinationdevice, and the binarizer 2 corresponds to a binarizer.

1. A picture angle detection apparatus for detecting an angle of apicture related to a pixel to be interpolated in each interpolationscanning line between scanning lines based on an input video signal,comprising: a binary pattern generator that binarizes said input videosignal in a predetermined detection region including a plurality ofscanning lines and said pixel to be interpolated to generate a binarypattern; a reference pattern generator that generates binary pictureshaving different directions as a plurality of reference patterns; acomparator that compares the binary pattern generated by said binarypattern generator with each of the plurality of reference patternsgenerated by said reference pattern generator to detect the angle of thepicture related to said pixel to be interpolated based on a comparisonresult; and a shape detector that detects the shape of the picture basedon a combination of the angle of the picture detected by said comparatorrelated to said pixel to be interpolated and angles of the picturedetected in upper and lower interpolation scanning lines, and when theangle of the picture detected by said comparator related to said pixelto be interpolated is between the angle of the picture detected in theupper interpolation scanning line and the angle of the picture detectedin the lower interpolation scanning line, and the absolute value of theangle of the picture detected in the upper interpolation scanning lineis larger than the absolute value of the angle of the picture detectedin the lower interpolation scanning line, said shape detector outputs ashape detection signal indicating that the shape of the picture isconvex toward the lower right, when the angle of the picture detectedrelated to said pixel to be interpolated, and the angle of the picturedetected in the upper interpolation scanning line and the angle of thepicture detected in the lower interpolation scanning line are positivevalues, and said shape detector outputs a shape detection signalindicating that the shape of the picture is convex toward the lowerleft, when the angle of the picture detected related to said pixel to beinterpolated, and the angle of the picture detected in the upperinterpolation scanning line and the angle of the picture detected in thelower interpolation scanning line are negative values, and when theangle of the picture detected by said comparator related to said pixelto be interpolated is between the angle of the picture detected in theupper interpolation scanning line and the angle of the picture detectedin the lower interpolation scanning line, and the absolute value of theangle of the picture detected in the upper interpolation scanning lineis smaller than the absolute value of the angle of the picture detectedin the lower interpolation scanning line, said shape detector outputs ashape detection signal indicating that the shape of the picture isconvex toward the upper left, when the angle of the picture detectedrelated to said pixel to be interpolated, and the angle of the picturedetected in the upper interpolation scanning line and the angle of thepicture detected in the lower interpolation scanning line are positivevalues, and said shape detector outputs a shape detection signalindicating that the shape of the picture is convex toward the upperright, when the angle of the picture detected related to said pixel tobe interpolated, and the angle of the picture detected in the upperinterpolation scanning line and the angle of the picture detected in thelower interpolation scanning line are negative values.
 2. A pictureangle detection apparatus for detecting an angle of a picture related toa pixel to be interpolated in each interpolation scanning line betweenscanning lines based on an input video signal, comprising: a binarypattern generator that binarizes said input video signal in apredetermined detection region including a plurality of scanning linesand said pixel to be interpolated to generate a binary pattern; areference pattern generator that generates binary pictures havingdifferent directions as a plurality of reference patterns; a comparatorthat compares the binary pattern generated by said binary patterngenerator with each of the plurality of reference patterns generated bysaid reference pattern generator to detect the angle of the picturerelated to said pixel to be interpolated based on a comparison result;and a shape detector that detects the shape of the picture based on acombination of the angle of the picture detected by said comparatorrelated to said pixel to be interpolated and angles of the picturedetected in upper and lower interpolation scanning lines, wherein whensaid shape detector detects that the shape of the picture is an arc,said detector outputs a shape detection signal indicating the directionof the inside of the arc.
 3. A picture angle detection apparatus fordetecting an angle of a picture related to a pixel to be interpolated ineach interpolation scanning line between scanning lines based on aninput video signal, comprising: a binary pattern generator thatbinarizes said input video signal in a predetermined detection regionincluding a plurality of scanning lines and said pixel to beinterpolated to generate a binary pattern; a reference pattern generatorthat generates binary pictures having different directions as aplurality of reference patterns; a comparator that compares the binarypattern generated by said binary pattern generator with each of theplurality of reference patterns generated by said reference patterngenerator to detect the angle of the picture related to said pixel to beinterpolated based on a comparison result; and a shape detector thatdetects the shape of the picture based on a combination of the angle ofthe picture detected by said comparator related to said pixel to beinterpolated and angles of the picture detected in upper and lowerinterpolation scanning lines, wherein said binary pattern generatorcomprises: a threshold value calculation device that calculates athreshold value for binarization based on the luminance of a videosignal in said detection region; and a binarizer that binarizes saidinput video signal using the threshold value calculated by saidthreshold value calculation device to generate said binary pattern.
 4. Apicture angle detection apparatus for detecting an angle of a picturerelated to a pixel to be interpolated in each interpolation scanningline between scanning lines based on an input video signal, comprising:a binary pattern generator that binarizes said input video signal in apredetermined detection region including a plurality of scanning linesand said pixel to be interpolated to generate a binary pattern; areference pattern generator that generates binary pictures havingdifferent directions as a plurality of reference patterns; a comparatorthat compares the binary pattern generated by said binary patterngenerator with each of the plurality of reference patterns generated bysaid reference pattern generator to detect the angle of the picturerelated to said pixel to be interpolated based on a comparison result;and a shape detector that detects the shape of the picture based on acombination of the angle of the picture detected by said comparatorrelated to said pixel to be interpolated and angles of the picturedetected in upper and lower interpolation scanning lines, and adetermining device that determines whether or not the luminancedistribution in the horizontal direction of each scanning line is in theform of a monotonous increase or a monotonous decrease in the videosignal in said detection region, wherein said comparator does notcompare said binary pattern with each of said plurality of referencepatterns when said luminance distribution is neither in the form of amonotonous increase nor a monotonous decrease.
 5. A picture angledetection apparatus for detecting an angle of a picture related to apixel to be interpolated in each interpolation scanning line betweenscanning lines based on an input video signal, comprising: a binarypattern generator that binarizes said input video signal in apredetermined detection region including a plurality of scanning linesand said pixel to be interpolated to generate a binary pattern; areference pattern generator that generates binary pictures havingdifferent directions as a plurality of reference patterns; a comparatorthat compares the binary pattern generated by said binary patterngenerator with each of the plurality of reference patterns generated bysaid reference pattern generator to detect the angle of the picturerelated to said pixel to be interpolated based on a comparison result;and a shape detector that detects the shape of the picture based on acombination of the angle of the picture detected by said comparatorrelated to said pixel to be interpolated and angles of the picturedetected in upper and lower interpolation scanning lines, and a contrastdetector that detects a contrast in a video signal in said detectionregion, wherein said comparator does not compare said binary patternwith each of said plurality of reference patterns when the contrastdetected by said contrast detector is smaller than a predeterminedvalue.
 6. A picture angle detection apparatus for detecting an angle ofa picture related to a pixel to be interpolated in each interpolationscanning line between scanning lines based on an input video signal,comprising: a binary pattern generator that binarizes said input videosignal in a predetermined detection region including a plurality ofscanning lines and said pixel to be interpolated to generate a binarypattern; a reference pattern generator that generates binary pictureshaving different directions as a plurality of reference patterns; acomparator that compares the binary pattern generated by said binarypattern generator with each of the plurality of reference patternsgenerated by said reference pattern generator to detect the angle of thepicture related to said pixel to be interpolated based on a comparisonresult; and a shape detector that detects the shape of the picture basedon a combination of the angle of the picture detected by said comparatorrelated to said pixel to be interpolated and angles of the picturedetected in upper and lower interpolation scanning lines, wherein theplurality of reference patterns each include a first pixel row arrangedin a scanning line above said pixel to be interpolated and a secondpixel row arranged in a scanning line below said pixel to beinterpolated, and wherein said first pixel row has one transition pointfrom a first pixel value to a second pixel value, said second pixel rowhas one transition point from a first pixel value to a second pixelvalue, and the transition direction from the first pixel value to thesecond pixel value in said first pixel row and the transition directionfrom the first pixel value to the second pixel value in the second pixelrow are the same.
 7. A scanning lines interpolation apparatus,comprising: a picture angle detection apparatus that detects the angleand shape of a picture related to a pixel to be interpolated based on aninput video signal; and an interpolation circuit that selects pixels tobe used for interpolation based on the angle and shape detected by saidpicture angle detection apparatus, and calculates the value of saidpixel to be interpolated using the selected pixels to generate aninterpolation scanning line, said picture angle detection apparatusincluding: a binary pattern generator that binarizes said input videosignal in a predetermined detection region including a plurality ofscanning lines and said pixel to be interpolated in each said scanningline to generate a binary pattern; a reference pattern generator thatgenerates binary pictures having different directions as a plurality ofreference patterns; a comparator that compares the binary patterngenerated by said binary pattern generator with each of the plurality ofreference patterns generated by said reference pattern generator todetect the angle of the picture related to said pixel to be interpolatedbased on a result of comparison; and a shape detector that detects theshape of the picture based on a combination of the angle of the picturedetected by said comparator related to said pixel to be interpolated andangles of the picture detected in upper and lower interpolation scanninglines, and when the angle of the picture detected by said comparatorrelated to said pixel to be interpolated is between the angle of thepicture detected in the upper interpolation scanning line and the angleof the picture detected in the lower interpolation scanning line, andthe absolute value of the angle of the picture detected in the upperinterpolation scanning line is larger than the absolute value of theangle of the picture detected in the lower interpolation scanning line,said shape detector outputs a shape detection signal indicating that theshape of the picture is convex toward the lower right, when the angle ofthe picture detected related to said pixel to be interpolated, and theangle of the picture detected in the upper interpolation scanning lineand the angle of the picture detected in the lower interpolationscanning line are positive values, and said shape detector outputs ashape detection signal indicating that the shape of the picture isconvex toward the lower left, when the angle of the picture detectedrelated to said pixel to be interpolated, and the angle of the picturedetected in the upper interpolation scanning line and the angle of thepicture detected in the lower interpolation scanning line are negativevalues, and when the angle of the picture detected by said comparatorrelated to said pixel to be interpolated is between the angle of thepicture detected in the upper interpolation scanning line and the angleof the picture detected in the lower interpolation scanning line, andthe absolute value of the angle of the picture detected in the upperinterpolation scanning line is smaller than the absolute value of theangle of the picture detected in the lower interpolation scanning line,said shape detector outputs a shape detection signal indicating that theshape of the picture is convex toward the upper left, when the angle ofthe picture detected related to said pixel to be interpolated, and theangle of the picture detected in the upper interpolation scanning lineand the angle of the picture detected in the lower interpolationscanning line are positive values, and said shape detector outputs ashape detection signal indicating that the shape of the picture isconvex toward the upper right, when the angle of the picture detectedrelated to said pixel to be interpolated, and the angle of the picturedetected in the upper interpolation scanning line and the angle of thepicture detected in the lower interpolation scanning line are negativevalues.
 8. A scanning lines interpolation apparatus, comprising: apicture angle detection apparatus that detects the angle and shape of apicture related to a pixel to be interpolated based on an input videosignal; and an interpolation circuit that selects pixels to be used forinterpolation based on the angle and shape detected by said pictureangle detection apparatus, and calculates the value of said pixel to beinterpolated using the selected pixels to generate an interpolationscanning line, said picture angle detection apparatus including: abinary pattern generator that binarizes said input video signal in apredetermined detection region including a plurality of scanning linesand said pixel to be interpolated in each said scanning line to generatea binary pattern; a reference pattern generator that generates binarypictures having different directions as a plurality of referencepatterns; a comparator that compares the binary pattern generated bysaid binary pattern generator with each of the plurality of referencepatterns generated by said reference pattern generator to detect theangle of the picture related to said pixel to be interpolated based on aresult of comparison; and a shape detector that detects the shape of thepicture based on a combination of the angle of the picture detected bysaid comparator related to said pixel to be interpolated and angles ofthe picture detected in upper and lower interpolation scanning lines,wherein when said shape detector detects that the shape of the pictureis an arc, said detector outputs a shape detection signal indicating thedirection of the inside of the arc, and wherein said interpolationcircuit selects pixels to be used for interpolation from the inside ofthe arc based on the shape detection signal output from the shapedetector and calculates the value of said pixel to be interpolated usingthe selected pixels to generate an interpolation scanning line.
 9. Ascanning lines interpolation apparatus, comprising: a picture angledetection apparatus that detects the angle and shape of a picturerelated to a pixel to be interpolated based on an input video signal;and an interpolation circuit that selects pixels to be used forinterpolation based on the angle and shape detected by said pictureangle detection apparatus, and calculates the value of said pixel to beinterpolated using the selected pixels to generate an interpolationscanning line, said picture angle detection apparatus including: abinary pattern generator that binarizes said input video signal in apredetermined detection region including a plurality of scanning linesand said pixel to be interpolated in each said scanning line to generatea binary pattern; a reference pattern generator that generates binarypictures having different directions as a plurality of referencepatterns; a comparator that compares the binary pattern generated bysaid binary pattern generator with each of the plurality of referencepatterns generated by said reference pattern generator to detect theangle of the picture related to said pixel to be interpolated based on aresult of comparison; and a shape detector that detects the shape of thepicture based on a combination of the angle of the picture detected bysaid comparator related to said pixel to be interpolated and angles ofthe picture detected in upper and lower interpolation scanning lines,wherein when said shape detector detects that the shape of the pictureis an arc, said detector outputs a shape detection signal indicating thedirection of the inside of the arc, and wherein said interpolationcircuit selects positions shifted in the direction of the inside of thearc by 0.5 pixel from positions in the upper and lower scanning lines inthe direction of the angle of the picture detected for the pixel to beinterpolated and calculates the value of said pixel to be interpolatedusing the values of the pixels in the selected positions.
 10. A pictureangle detection method for detecting an angle of a picture related to apixel to be interpolated in each interpolation scanning line betweenscanning lines based on an input video signal, comprising: binarizingsaid input video signal in a predetermined detection region including aplurality of scanning lines and said pixel to be interpolated togenerate a binary pattern; generating binary pictures having differentdirections as a plurality of reference patterns; comparing saidgenerated binary pattern with each of said generated plurality ofreference patterns to detect the angle of the picture related to saidpixel to be interpolated based on a comparison result; and detecting theshape of the picture based on a combination of the angle of saiddetected picture related to said pixel to be interpolated and angles ofthe picture detected in upper and lower interpolation scanning lines,and when the angle of the picture detected by the comparing related tosaid pixel to be interpolated is between the angle of the picturedetected in the upper interpolation scanning line and the angle of thepicture detected in the lower interpolation scanning line, and theabsolute value of the angle of the picture detected in the upperinterpolation scanning line is larger than the absolute value of theangle of the picture detected in the lower interpolation scanning line,outputting a shape detection signal indicating that the shape of thepicture is convex toward the lower right, when the angle of the picturedetected related to said pixel to be interpolated, and the angle of thepicture detected in the upper interpolation scanning line and the angleof the picture detected in the lower interpolation scanning line arepositive values, and the outputting of the shape detection signalindicating that the shape of the picture is convex toward the lowerleft, when the angle of the picture detected related to said pixel to beinterpolated, and the angle of the picture detected in the upperinterpolation scanning line and the angle of the picture detected in thelower interpolation scanning line are negative values, and when theangle of the picture detected by the comparing related to said pixel tobe interpolated is between the angle of the picture detected in theupper interpolation scanning line and the angle of the picture detectedin the lower interpolation scanning line, and the absolute value of theangle of the picture detected in the upper interpolation scanning lineis smaller than the absolute value of the angle of the picture detectedin the lower interpolation scanning line, outputting a shape detectionsignal indicating that the shape of the picture is convex toward theupper left, when the angle of the picture detected related to said pixelto be interpolated, and the angle of the picture detected in the upperinterpolation scanning line and the angle of the picture detected in thelower interpolation scanning line are positive values, and theoutputting of the shape detection signal indicating that the shape ofthe picture is convex toward the upper right, when the angle of thepicture detected related to said pixel to be interpolated, and the angleof the picture detected in the upper interpolation scanning line and theangle of the picture detected in the lower interpolation scanning lineare negative values.